Simplified diagram of key steps during the influenza virus life cycle highlighting events that are regulated by PTMs to viral or host proteins. The specific modifications, target proteins, and references are listed for each step. Two processes are highlighted in depth; these examples were chosen because the PTMs and causative host enzymes are known and the modifications have discrete effects on replication. In addition, a large number of PTMs have been identified on viral proteins, but no discrete function has yet been assigned [14]. Ac, acetylation; ADPr, ADP-ribosylation; cRNA, plus-sense genomic RNA; dsRNA, double-stranded RNA; Glycos., N-linked glycosylation; ISG15, ISGylation; Nedd8, neddylation; NP, nucleoprotein; NS1, nonstructural protein 1; PO4, phosphorylation; PTM, post-translational modification; RNP, ribonucleoprotein complex; SA, sialic acid; SUMO, SUMOylation; Ub, ubiquitin and ubiquitination; vRNA, minus-sense genomic RNA.